The proposed Program of Projects comprises several investigations having overlapping interests and sharing in common some of the experimental approaches. The projects all have similar objectives in the general area of mental retardation and other neurological diseases seeking improved diagnostic prcedures, new therapeutic measures, and elucidation of specific biochemical defects. The investigations encompass broadly the disciplines of biochemistry and genetics with specific projects ranging from basic to clinical in nature. The several projects encompass the areas of (1) induced and inherited abnormalities in heme biosynthesis especially relating to iron nutrition, lead toxicity and the porphyrias, (2) the pathogenesis and prevention of kernicterus as a consequence of hyperbilirubinemia, (3) genetic aspects of amino acid metabolism and the elucidation of the biochemical lesions in certain of these diseases, (4) the pathologic and metabolic aspects of the mucopolysaccharidoses with particular attention to new thrapeutic measures, and (5) genetic and biochemical studies of the leukodystrophies.